Abstract: Disclosed is an optical waveguide element that includes first and second optical waveguides (11, 12) which are formed to have different waveguide modes of guided lights, whose polarized waves are different. First optical waveguide (11) includes directional coupling region (13) and, second optical waveguide (12) includes incident side waveguide (12a), which has directional coupling region (13) and which is provided in parallel with first optical waveguide (11), and second optical waveguide (12) includes exit side waveguide (12b), which is extended from incident side waveguide (12a) and which is bent in the direction that recedes from first optical waveguide (11).

Abstract: Disclosed in a method and a device in which a wave number of light in the waveguide mode of a photonic crystal optical waveguide is matched with that of the incident light, or a intensity ratio of electric field to magnetic field of the light in the waveguide mode of the photonic crystal optical waveguide is matched with that of the incident light, and furthermore, in addition to the method above, the distribution of light intensity on the incident end surface in the waveguide mode of the photonic crystal optical waveguide is matched with that of the incident light. A photonic crystal optical waveguide and channel optical waveguide are joined together, and the structure of the channel optical waveguide is wedge shaped in the joint section.

Abstract: Disclosed is an optical waveguide element that includes first and second optical waveguides (11, 12) which are formed to have different waveguide modes of guided lights, whose polarized waves are different. First optical waveguide (11) includes directional coupling region (13) and, second optical waveguide (12) includes incident side waveguide (12a), which has directional coupling region (13) and which is provided in parallel with first optical waveguide (11), and second optical waveguide (12) includes exit side waveguide (12b), which is extended from incident side waveguide (12a) and which is bent in the direction that recedes from first optical waveguide (11).

Abstract: Disclosed in a method and a device in which a wave number of light in the waveguide mode of a photonic crystal optical waveguide is matched with that of the incident light, or a intensity ratio of electric field to magnetic field of the light in the waveguide mode of the photonic crystal optical waveguide is matched with that of the incident light, and furthermore, in addition to the method above, the distribution of light intensity on the incident end surface in the waveguide mode of the photonic crystal optical waveguide is matched with that of the incident light. A photonic crystal optical waveguide and channel optical waveguide are joined together, and the structure of the channel optical waveguide is wedge shaped in the joint section.

Abstract: Disclosed in a method and a device in which a wave number of light in the waveguide mode of a photonic crystal optical waveguide is matched with that of the incident light, or a intensity ratio of electric field to magnetic field of the light in the waveguide mode of the photonic crystal optical waveguide is matched with that of the incident light, and furthermore, in addition to the method above, the distribution of light intensity on the incident end surface in the waveguide mode of the photonic crystal optical waveguide is matched with that of the incident light. A photonic crystal optical waveguide and channel optical waveguide are joined together, and the structure of the channel optical waveguide is wedge shaped in the joint section.

Abstract: The invention provides a method for selective growth of semiconductor crystals, including the step of forming a semiconductor layer in a selected region of a semiconductor substrate by using a mask, the semiconductor layer being controlled with respect to atomic ordering or natural super lattice (NSL). It is possible by the invention to control the energy gap, optical anisotropy and electrically conductive anisotropy of a semiconductor layer, and also possible by the invention to carry out two-dimensional control of material properties in a substrate in accordance with a pattern of a mask.

Abstract: A heterojunction semiconductor device has a plurality of ordered phase alloy layers. Either the whole or a part of each of the ordered phase alloy layers has a crystal structure (triple-period structure) in which the ordered alloy is of a composition corresponding to the [111]A direction and an anion composition modulation period that is triple that of a disordered structure. The double-period structure may alternatively be used. The triple-period or double-period structure applied to the layer structure of the heterostructure semiconductor device results in a reduction of the bandgap.

Abstract: In a semiconductor laser, an active layer includes a semiconductor layer having the ordered structure along the [-1,1,1] direction or along the [1,-1,1] direction. By the action of the ordered structure, the electric vector of the recombination light generated in the active layer is concentrated in the (-1,1,1) plane or the (1,-1,1) plane. Alternatively, the semiconductor layer has not only the ordered structure along the [-1,1,1] direction or along the [1,-1,1] direction, but also the compressive strain in the (0,0,1) plane. By the action of the ordered structure and the compressive strain, the recombination light generated in the active layer is emitted in the (1,1,0) plane. As a result, the recombination light effectively gives a gain to the oscillation mode. Thus, the oscillation threshold current of the semiconductor laser is reduced, and the laser characteristics is improved.

Abstract: In a visible light semiconductor laser with (Al.sub.x Ga.sub.1-x).sub.0.5 In.sub.0.5 P (0.ltoreq.x .ltoreq.1) crystal layers and a process for growing an(Al.sub.x Ga.sub.1-x).sub.0.5 In.sub.0.5 P (0.ltoreq.x.ltoreq.1) crystal, a GaAs substrate on which (Al.sub.x Ga.sub.1-x).sub.0.5 In.sub.0.5 P is grown in an epitaxial method selected from MOVPE and MBE provides one selected from a (110) plane, a plane equivalent to the (110) plane, a (111) plane, and a plane equivalent to the (111) plane as a main plane for a crystal growth of (Al.sub.x Ga.sub.1-x).sub.0.5 In.sub.0.5 P. As a result, a bandgap energy Eg of the (Al.sub.x Ga.sub.1-x).sub.0.5 In.sub.0.5 P crystal can be the maximum value inherent to the mixed crystal independent on a growth temperature and a V/III ratio.